Microprocessor based controllers have been developed in recent years to assist in the preparation of properly cooked foods. Under program control, the electronic controller regulates the various operations of the cooking appliance during a cooking cycle, including the temperature of the cooking medium or grill platen, so as to insure properly cooked food. Today's cooking appliances require somewhat sophisticated electronic controllers to keep the cooking temperature at a desired temperature or the so-called “set point,” with as little overshoot as possible. To do so, however, the cooking appliance is calibrated so that the indicated temperature accurately corresponds to the actual temperature of the cooking medium, or the grill platen. Over time, changes in the appliance, such as in the temperature sensing probe or the electronics, or changes in the operating environment, will affect the temperature calibration, and hence the performance of the cooking appliance. Whatever the cause, it is apparent that the cooking appliance will need to be re-calibrated at some point, and more likely on a periodical basis, even daily.
To perform a calibration, an operator or service agent uses an external, temperature calibration probe, such as a thermocouple, to measure the actual temperature of the cooking medium, or grill platen. Even after calibration, it is still not uncommon for the actual temperature of the cooking medium or the grill platen to differ as much as 5–10° F. from that indicated by its internal temperature sensing probe.